This invention relates to an improved shuttleless loom, in particular of the type which utilizes one or more weft thread carriers moving along a closed path.
As is known, shuttleless looms, also called shuttleless Sulzer looms, have important advantages over traditional looms of the shuttle type. In fact, since the thread-carrying cop no longer needs to be carried through the shed in the shuttle, it becomes possible to considerably reduce the size of the weft thread carriers and, accordingly, the moving masses involved, which results in an increase of the throw velocity and of the production output over traditional looms.
Also known is, however, that along with such advantages, shuttleless or Sulzer-type looms have some significant drawbacks.
First of all, they require energy in considerable amounts: both the weft thread carrier throwing and, above all, the cyclic actuation of the throwing members--the latter involving particularly high momenta--imply a waste of energy which remains for the most part unused because the weft thread carriers and throwing members have to be brought back to rest after each throw.
Another drawback, and one of great practical importance, is the noisy operation of such looms, as due primarily to the fast reciprocating masses, which are continuously subjected to sudden restarts and stops.
Previous studies by the same Inventor have substantially solved such problems. For example, U.S. Pat. No. 4,015,642 discloses a loom wherein a weft thread carrier is redirected as it emerges from the shed, i.e. after being passed through the warp threads, along a return travel guide which takes it back without discontinuities of motion over a continuous closed path, at the shed entering area, exactly to the starting point.
The solutions disclosed in the cited patent have resulted in a surprisingly advantageous loom as regards efficiency, silent operation, reduced energy expenditure, and above all operating speed. In other terms, a loom has been provided which affords a much higher performance level than the best of conventional shuttleless looms. However, the cost of the loom proved to be directly related to its performance, namely a high one, and, furthermore specially critical was the tuning of those members which provide for the synchronization of the weft thread carrier throws to the sley movements.
In actual practice, the synchronization of the weft thread carrier throws requires expensive and quite sophisticated control devices, which are indeed practicable, as the numerous tests carried out have proved, but are unsuitable for application to looms which are not intended for specially high performance.
Another problem, also connected with the solutions taught in the cited patent by this same Inventor, is that such a loom cannot result from an adaptation of prior or existing conventional shuttleless looms, since the latter are inadequate to provide the required performance level, and too many and important are the machine members in need of being modified and replaced.
Thus, it can be seen that the conventional art has a remarkably important disadvantage, namely, there are no looms available which, for one aspect, can overcome at least most of the serious drawbacks connected with said conventional shuttleless looms, which require a considerable expenditure of energy for the intermittent operation of their members, in particular of their throwing members, and are too noisy in operation, and for another aspect, are not particularly so very expensive and complicated to tune, many looms being not intended for particularly high performance levels.
In practice, the current state of the art provides for no possibility to update with simple and inexpensive operations the large number of old-type shuttleless looms present in the field, in agreement with modern requisites which forbid excessive energy consumption and noise emission.